Differences in flavor and mouth feel of lettuce wraps vs. breads poses a problem for the chains that goes beyond the material costs. If you look at the ingredi

Differences in flavor and mouth feel of lettuce wraps vs. breads poses a problem for the chains that goes beyond the material costs. If you look at the ingredients of the typical hamburger bun sold at a supermarket, you'll notice that it's actually doubling as a delivery mechanism for additional sodium and soybean oil - it's very influential on the taste and texture of the sandwich. And when you remove the bun from the burger, you have a meat patty which tastes like any meat that's been fried or grilled. So because the bun allows the chains to distinguish themselves further, it's part of their brand identity, as well.